The present invention relates to broadcast receivers, that is to say receivers of broadcast electromagnetic waves modulated in amplitude or in frequency on emission by a sound or audio-frequency signal, and more especially to the arrangement of their control devices. It relates, more particularly, to so-called "radio" receivers and especially those intended to fitted to motor vehicles, called "car radios" and to the control devices thereof, free from any mechanical component.
In conventional "radio" and "car radio" receivers, the control devices comprise, more especially, an "on-off" switch which is either coupled to the shaft controlling the volume control potentiometer, which must be rotated, or controlled by a push-button, a volume control potentiometer with rotary or rectilinear translation shaft, a reactive element for tuning the resonant radio-frequency circuits and the local oscillator comprising several simultaneously variable reactances, such as multiple tuning capacitors, fixed to the same shaft or inductances with axial mobile cores and mechanically coupled control, and rotary wave range switches with push-buttons or keys. All these elements, as well as the tuning indicator with its dial, generally have a mechanical control and those with rotary shafts are manipulated by the user by means of rotary knobs which extend from the front face turned towards him.
Mechanical control elements such as volume or tuning voltage regulating potentiometers, when the variable reactance elements are formed by diodes ("varicap") whose capacity is variable as a function of their reverse biasing voltage, and multiple rotary capacitors or the mobile core coils are sources of mechanical and/or electrical (false contact) breakdowns and are subject to wear.
In so far as the receivers are concerned which are intended to be mounted on board motor vehicles so as to be accessible to the driver, whose case may be inserted in an opening formed in the dashboard, for example, the projecting parts which extend from the front face or facade of the receiver, such as rotary control knobs, are likely to cause injuries to the driver and/or passengers of the vehicle, particularly during sudden decelerations of this latter. Moreover, rotary control knobs, push-buttons and station indicators make the presence of a conventional car radio easily detectable by possible thieves.
The invention remedies the above-mentioned drawbacks by replacing the mechanical control and indication elements by static, entirely electronic, elements.
The invention provides a broadcast receiver with control devices entirely free of mechanical elements.